Endodontic instruments

ABSTRACT

A rotatable endodontic file for cleaning/shaping a tooth root canal, comprising: an elongated shaft having a proximal end portion, a distal end and a tapered working portion having a rotational axis, the working portion extending from said proximal portion to said distal end; the external surface of said shaft working portion having a plurality of at least two spirals, a plurality of parallelogram-shaped cross sections along the working portion, at least one of the plurality of parallelogram-shaped cross sections two C-shaped or concave geometries along two symmetrical sides or four C-shaped or concave geometries along all four sides, each parallelogram-shaped cross section having an acute angle and a center of mass that is located on the axis of rotation, each parallelogram-shaped cross section, wherein an acute angle of a first parallelogram-shaped cross section is different or the same as an acute angle of a second parallelogram-shaped cross section.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Divisional patent application of U.S. patent application Ser.No. 14/311,134, filed on Jun. 20, 2014, which claims the benefit of andpriority to U.S. Provisional Patent Application Ser. No. 61/837,312,filed on Jun. 20, 2013, which are herein incorporated by reference forall purposes.

FIELD OF INVENTION

The present invention relates to endodontic instruments.

BACKGROUND OF THE INVENTION

Endodontic instruments can be used for cleaning and enlarging theendodontic cavity space (“ECS”), also known as the root canal system ofa human tooth. The unprepared root canal is usually a narrow channelthat runs through the central portion of the root of the tooth. Cleaningand enlargement of the ECS can be necessitated by the death or necrosisof the dental pulp, which is the tissue that occupies that space in ahealthy tooth. This tissue can degenerate for a multitude of reasons,which include tooth decay, deep dental restorations, complete andincomplete dental fractures, traumatic injuries or spontaneous necrosisdue to the calcification and ischemia of the tissue, which usuallyaccompanies the ageing process. Similar to a necrotic or gangrenousappendix, the complete removal of this tissue is paramount, if noturgent, because of the subsequent development of infections or dentalabscesses, septicemia, and even death.

The root canal system of a human tooth is often narrow, curved andcalcified, and can be extremely difficult to negotiate or clean. Indeed,the conventional endodontic or root canal instruments currentlyavailable are frequently inadequate in the complete removal of the pulpand the efficient enlargement of the ECS. Furthermore, they are usuallypredisposed to breakage, causing further destruction to the tooth.Broken instruments are usually difficult, if not impossible to remove,often necessitating the removal of the tooth. Injury to the tooth, whichoccurs as the result of a frank perforation or alteration of the naturalanatomy of the ECS, can also lead to failure of the root canal and toothloss.

The unprepared root canal of the tooth usually begins as a narrow andrelatively parallel channel. The portal of entry or the orifice and theportal of exit or foramen are relatively equal in diameter. Toaccommodate complete cleaning and filling of the canal and to preventfurther infection, the canal must usually be prepared. The endodonticcavity preparation (“ECP”) generally includes progressively enlargingthe orifice and the body of the canal, while leaving the foramenrelatively small. The result is usually a continuous cone-shapedpreparation.

In general, endodontic instruments are used to prepare the endodonticcavity space as described above. Endodontic instruments can include handinstruments and engine driven instruments. The latter can but need notbe a rotary instrument. Combinations of both conventional hand andengine-driven rotary instruments are usually required to perform an ECPsuccessfully and safely.

An endodontic instrument may include a shaft that includes a tip and ashank. The endodontic instrument also includes grooves that spiralaround the shaft. The grooves are referred to in the instantspecification as flutes, (FIG. 1).

The cross section of a file shows flutes (FIG. 2).

The flutes are generally the spacing on both sides of a helicalstructure (or helix) that spirals around the shaft. The bottom portionof a flute—seen as a line or curve is referred to in the instantspecification as a spline. The portion of a spline that comes intocontact with a surface being cut during cutting will be referred to inthe instant specification as a radial land.

A flute of an endodontic instrument usually includes a sharpened edgeconfigured for cutting. Cutting Edge of FIG. 3 is an example of such acutting edge.

Generally, an instrument having right-handed cutting edges is one thatwill cut or remove material when rotated clockwise, as viewed from shankto tip. In this specification, a direction of rotation will be specifiedas viewed from the shank to the tip of the instrument. The cut directionof rotation for a right handed endodontic instrument is clockwise. Aninstrument having left-handed cutting edges is one that will cut orremove material when rotated counter-clockwise. The cut direction ofrotation, in this case, is counter-clockwise.

An endodontic instrument includes a working portion, which is theportion that can cut or remove material. The working portion istypically the portion along the shaft that is between the tip of theinstrument and the shank end of the flutes. The working portion is alsoreferred to in this specification as the cutting portion, and theworking length as the cutting or working length.

Hand instruments are typically manufactured from metal wire blanks ofvarying sizes. The metallurgical properties of these wires, in general,have been engineered to produce a wide range of physical properties.These wires are usually then twisted or cut to produce specific shapesand styles. Examples of hand instruments include K-type, H-type, andR-type hand instruments. The barbed broach is manufactured from softiron wire that is tapered and notched to form barbs or rasps along itssurface. These instruments are generally used in the gross removal ofpulp tissue or debris from the root canal system. Another R-type file isa rat-tail file.

K-type instruments in current usage include reamers and K-files. K filesare generally available in carbon steel, stainless steel, and morerecently, an alloy of nickel-titanium. To fabricate a K-type instrument,a round wire of varying diameters is usually grounded into three orfour-sided pyramidal blanks and then rotated or twisted into theappropriate shapes. These shapes are specified and controlled by theAmerican National Standards Institute (“ANSI”) and the InternationalStandards Organization (“ISO”). The manufacturing processes for reamersand files are similar; except however, files usually have a greaternumber of flutes per unit length than reamers. Reamers are used in arotational direction only, whereas files can be used in a rotational orpush-pull fashion. Files made from three-sided or triangular blanks havesmaller cross sectional areas than files made from four-sided blanks.Thus, these instruments are usually more flexible and less likely tofracture. They also can display larger clearance angles and are moreefficient during debridement. Triangular files, therefore, are generallyconsidered more desirable for hand instrumentation.

H-type files are usually manufactured by grinding flutes into taperedround metal blanks to form a series of intersecting cones. H-type filescan usually cut only in the pull direction (i.e., a pull stroke).Primarily because they have positive cutting angles, H-type files can beextremely efficient cutting instruments.

Hand instruments are usually manufactured according to guidelines of theANSI and the ISO, which specified that a working portion of aninstrument be 16 mm in length. ANSI and ISO further specified that afirst diameter or D.sub.1 of the instrument, be 1 mm from the tip orD.sub.0. Other ANSI and ISO specifications require that: instrumentshave a standard taper of 0.02 mm per mm along the working portion; thetip maintains a pyramidal shape no greater than 75 degree. in linearcross section; and hand instruments are available in 21, 25, and 31 mmlengths.

In addition to the hand instruments described above, there are rotaryinstruments that are usually motor driven. G-type drills are usuallyavailable in carbon or stainless steel. As is typical, the G-type drill300 shown includes a short flame-shaped head attached to a long shank.The flutes, in this instance, have U-shaped splines. The instrumentincludes cutting edges that have negative rake-angles. In general, arake angle is the angle between the leading edge of a cutting tool and aperpendicular to the surface being cut. Rake angle is further describedbelow. The flame-shaped head includes a non-cutting surface to preventperforation. The instrument is usually used as a side-cutting instrumentonly. The instrument is relatively rigid and, therefore, may incurproblem while used in a curved space, for example, the ECS.

The present invention discloses endodontic instruments havingderivatives of parallelogram-shaped cross sections in an attempt toovercome the deficiencies of predicate endodontic files as well as filesof U.S. Pat. No. 4,260,379, which discloses a preform parallelogram wireblank (spiral free) that is then twisted to create the spiral in thefiles.

SUMMARY OF INVENTION

The present invention seeks to improve upon prior root canal cleaningand/or enlarging systems by providing an improved rotatable endodonticfile for cleaning/shaping a tooth root canal, comprising: an elongatedshaft having a proximal end portion, a distal end and a tapered workingportion having a rotational axis, the working portion extending fromsaid proximal portion to said distal end; the external surface of saidshaft working portion having a plurality of at least two spirals, aplurality of parallelogram-shaped cross sections along the workingportion, each parallelogram-shaped cross sections having an acute angleand an axis of rotation that is centered such that the cross sectioncenter of mass (centroid) is located at the axis of rotation, wherein anacute angle of a first parallelogram-shaped cross section is differentfrom an acute angle of a second parallelogram-shaped cross section.

In another aspect, the present invention contemplates a rotatableendodontic file for cleaning/shaping a tooth root canal, comprising: anelongated shaft having a proximal end portion, a distal end and atapered working portion having a rotational axis, the working portionextending from said proximal portion to said distal end; the externalsurface of said shaft working portion having a plurality of at least twospirals, a plurality of parallelogram-shaped cross sections along theworking portion, each parallelogram-shaped cross section having an acuteangle and an axis of rotation that is asymmetric such that the center ofmass (centroid) is not located at the axis of rotation, wherein an acuteangle of a first parallelogram-shaped cross section is the same ordifferent than an acute angle of a second parallelogram-shaped crosssection of the working portion.

In another aspect, the present invention contemplates a rotatableendodontic file for cleaning/shaping a tooth root canal, comprising: anelongated shaft having a proximal end portion, a distal end and atapered working portion having a rotational axis, the working portionextending from said proximal portion to said distal end; the externalsurface of said shaft working portion having a plurality of at least twospirals, a plurality of parallelogram-shaped cross sections along theworking portion, at least one of the plurality of parallelogram-shapedcross sections two C-shaped or concave geometries along two symmetricalsides or four C-shaped or concave geometries along all four sides, eachparallelogram-shaped cross section having an acute angle and a center ofmass (centroid) that is located on the axis of rotation, eachparallelogram-shaped cross section, wherein an acute angle of a firstparallelogram-shaped cross section is different or the same as an acuteangle of a second parallelogram-shaped cross section.

In another aspect, the present invention contemplates a rotatableendodontic file for cleaning/shaping a tooth root canal, comprising: anelongated shaft having a proximal end portion, a distal end and atapered working portion having a rotational axis, the working portionextending from said proximal portion to said distal end; the externalsurface of said shaft working portion having a plurality of at least twospirals, a plurality of parallelogram-shaped cross sections that extendalong the working portion, at least one of the parallelogram-shapedcross sections having one, two, three, or four C-shaped or concavegeometries along one, two, three, or four sides, wherein eachparallelogram-shaped cross section having an acute angle and a center ofmass (centroid) is not located on the axis of rotation, and wherein anacute angle of a first parallelogram-shaped cross section is differentor the same as an acute angle of a second parallelogram-shaped crosssection.

In yet another aspect, any of the aspects of the present invention maybe further characterized by one or any combination of the followingfeatures: wherein the acute angle of the first parallelogram-shapedcross section is towards the proximal end and is larger than the acuteangle of the second parallelogram-shaped cross section that is towardsthe distal end; wherein the acute angles range between 50 degrees and 85degrees, wherein the endodontic file is composed of a material selectedfrom the group consisting of a Nitinol based material, a Cu basedmaterial, a titanium based material and a stainless steel basedmaterial; wherein the material is processed by high temperature, coldtemperatures and/or strain; wherein the acute angle of the firstparallelogram-shaped cross section is larger towards the proximal endthan the acute angle of the second parallelogram-shaped cross sectiontowards the distal end; wherein the acute angles range between 50degrees and 85 degrees; wherein the acute angles of the first and secondparallelogram-shaped cross sections range between 50 degrees and 85degrees; wherein the material is processed by high temperature fromabout 100° C. to 600° C., 100° C. to 480° C., or about 100° C. to 180°C.; wherein the material is processed by cold temperature from about−100° C. to 10° C., −60° C. to 10° C., or about 0° C. to 10° C.; whereinthe material is processed by strain and/or stress from about 1% to 10%,from about 2% to 9%, or from about 2% to 8%; wherein the acute anglesdecrease from the proximal end to the distal end and range between 50degrees and 85 degrees, wherein a plurality of acute angles towards theproximal end are larger than a plurality of acute angles towards thedistal end; wherein the a plurality of acute angles towards the proximalend are the same while being different than a plurality of acute anglestowards the distal end; wherein the endodontic file is a variabletapered file; wherein the endodontic file is a constant tapered file; orany combination thereof.

It should be appreciated that the above referenced aspects and examplesare non-limiting as others exist with the present invention, as shownand described herein. For example, any of the above-mentioned aspects orfeatures of the invention may be combined to form other uniqueconfigurations, as described herein, demonstrated in the drawings, orotherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a first embodiment of an endodontic fileof the present invention.

FIG. 2 is a perspective view of a second embodiment of an endodonticfile of the present invention.

FIG. 3 is a perspective view of a third embodiment of an endodontic fileof the present invention.

FIG. 4 is a perspective view of a forth embodiment of an endodontic fileof the present invention.

FIG. 4A is a parallelogram-shaped cross section taken across 4A-4A ofthe endodontic file shown if FIG. 4.

FIG. 5 is a perspective view of a fifth embodiment of an endodontic fileof the present invention.

FIG. 5A is a parallelogram-shaped cross section taken across 5A-5A ofthe endodontic file shown in FIG. 5.

FIG. 6 is a perspective view of a sixth embodiment of an endodontic fileof the present invention.

FIG. 6A is a first parallelogram-shaped cross section taken across 6A-6Aof the endodontic file shown in FIG. 6.

FIG. 6B is a second parallelogram-shaped cross section taken across6B-6B of the endodontic file shown in FIG. 6.

FIG. 7 is a perspective view of a seventh embodiment of an endodonticfile of the present invention.

FIG. 7A is a first parallelogram-shaped cross section taken across 7A-7Aof the endodontic file shown in FIG. 7.

FIG. 7B is a second parallelogram-shaped cross section taken across7B-7B of the endodontic file shown in FIG. 7.

FIG. 8 is a perspective view of a eighth embodiment of an endodonticfile of the present invention.

FIG. 8A is a parallelogram-shaped cross section taken across 8A-8A ofthe endodontic file shown in FIG. 8.

FIG. 9 is a perspective view of a ninth embodiment of an endodontic fileof the present invention.

FIG. 9A is a first parallelogram-shaped cross section taken across 9A-9Aof the endodontic file shown in FIG. 9.

FIG. 9B is a second parallelogram-shaped cross section taken across9B-9B of the endodontic file shown in FIG. 9.

FIG. 10 is a perspective view of a tenth embodiment of an endodonticfile of the present invention.

FIG. 10A is a parallelogram-shaped cross section taken across 10A-10A ofthe endodontic file shown in FIG. 10.

FIG. 11 is a perspective view of an eleventh embodiment of an endodonticfile of the present invention.

FIG. 11A is a first parallelogram-shaped cross section taken across11A-11A of the endodontic file shown in FIG. 11.

FIG. 11B is a second parallelogram-shaped cross section taken across11B-11B of the endodontic file shown in FIG. 11.

FIG. 12 is a perspective view of a twelfth embodiment of an endodonticfile of the present invention.

FIG. 12A is a first parallelogram-shaped cross section taken across12A-12A of the endodontic file shown in FIG. 12.

FIG. 12B is a second parallelogram-shaped cross section taken across12B-12B of the endodontic file shown in FIG. 12.

FIG. 12C is a third parallelogram-shaped cross section taken across12C-12C of the endodontic file shown in FIG. 12.

FIG. 12D is a forth parallelogram-shaped cross section taken across12D-12D of the endodontic file shown in FIG. 12.

FIG. 12E is a fifth parallelogram-shaped cross section taken across12E-12E of the endodontic file shown in FIG. 12.

FIG. 12F is a sixth parallelogram-shaped cross section taken across12F-12F of the endodontic file shown in FIG. 12.

FIG. 12G is a seventh parallelogram-shaped cross section taken across12G-12G of the endodontic file shown in FIG. 12.

FIG. 12H is an eighth parallelogram-shaped cross section taken across12H-12H of the endodontic file shown in FIG. 12.

FIG. 12I is a ninth parallelogram-shaped cross section taken across12I-12I of the endodontic file shown in FIG. 12.

FIG. 12J is a tenth parallelogram-shaped cross section taken across12J-12J of the endodontic file shown in FIG. 12.

FIG. 12K is an eleventh parallelogram-shaped cross section taken across12K-12K of the endodontic file shown in FIG. 12.

FIG. 12L is a twelfth parallelogram-shaped cross section taken across12L-12L of the endodontic file shown in FIG. 12.

FIG. 12M is a thirteenth parallelogram-shaped cross section taken across12M-12M of the endodontic file shown in FIG. 12.

FIG. 12N is a fourteenth parallelogram-shaped cross section taken across12N-12N of the endodontic file shown in FIG. 12.

FIG. 12O is a fifteenth parallelogram-shaped cross section taken across12O-12O of the endodontic file shown in FIG. 12.

FIG. 13 is a perspective view of an eleventh embodiment of an endodonticfile of the present invention.

FIG. 13A is a first parallelogram-shaped cross section taken across13A-13A of the endodontic file shown in FIG. 13.

FIG. 13B is a second parallelogram-shaped cross section taken across13B-13B of the endodontic file shown in FIG. 13.

FIG. 13C is a third parallelogram-shaped cross section taken across13C-13C of the endodontic file shown in FIG. 13.

FIG. 13D is a forth parallelogram-shaped cross section taken across13D-13D of the endodontic file shown in FIG. 13.

FIG. 13E is a fifth parallelogram-shaped cross section taken across13E-13E of the endodontic file shown in FIG. 13.

FIG. 13F is a sixth parallelogram-shaped cross section taken across13F-13F of the endodontic file shown in FIG. 13.

FIG. 13G is a seventh parallelogram-shaped cross section taken across13G-13G of the endodontic file shown in FIG. 13.

FIG. 14 is a first chart showing Cutting Angle versus CuttingEfficiency.

FIG. 15 is a second chart showing Acute Angle of a File on Center versusVoid Volume.

FIG. 16 is a third chart showing Void Volume versus Cutting Efficiency.

FIG. 17 is a fourth chart showing Acute Angle of a File Off Centerversus Void Volume.

FIG. 18 is a first chart showing Cutting Angle of a File Off Centerversus Cutting Efficiency.

DETAILED DESCRIPTION OF THE INVENTION

The invention discloses several novel approaches to parallelogram-shapedcross section and derivatives of parallelogram-shaped cross section fordental instruments (e.g., endodontic instruments such as endodonticfiles). In this invention, the angles of the parallelogram are grounddirectly into the file and the acute and obtuse angles of theparallelogram-shaped cross section vary along the axis of the file (FIG.4).

Another variation of the parallelogram-shaped cross section containsC-shaped or concave geometries along one, two, three or four sides ofthe parallelogram (FIG. 5).

The invention discloses several novel approaches to parallelogram-shapedcross sections and derivatives of parallelogram-shaped cross section forendodontic files.

The first approach is a parallelogram-shaped cross section that has anaxis of rotation that is centered such that the center of mass(centroid) is located at the axis of rotation. In this embodiment, theacute angle is different along the length of the file; preferably, theacute angle is larger at the tip and decreases as it approaches theshank. For example, the tip cross section has an acute angle of 70degrees and decrease to an acute angle of 60 degrees as it approachesthe shank (FIG. 6).

The second approach is a parallelogram-shaped cross section that has anaxis of rotation that is off-centered such that the center of mass(centroid) is not located at the axis of rotation. This is sometimesknown as an asymmetric cross-section. In this embodiment the acute angleis different or the same along the length of the file. If the acuteangle is different along the length of the file; preferably the acuteangle is larger at the tip and decreases as it approaches the shank. Forexample, the tip cross section has an acute angle of 80 degrees anddecreases to an acute angle of 70 degrees as it approaches the shank(FIG. 7).

The third embodiment is a parallelogram-shaped cross section that has anaxis of rotation that is centered such that the center of mass(centroid) is located at the axis of rotation and has 2 or 4 C-shaped orconcave geometries along 2 symmetrical sides or all 4 sides of the crosssection (FIG. 8).

In this embodiment the acute angle is different or the same along thelength of the file. If the acute angles are different along the lengthof the file, preferably the acute angle is larger at the tip anddecreases as it approaches the shank. For example, the tip cross sectionhas an acute angle of 80 degrees and decrease to an acute angle of 70degrees as it approaches the shank (FIG. 9).

The fourth approach is a parallelogram-shaped cross section that has across section which is off-centered such that the center of mass(centroid) is not located at the axis of rotation (asymmetriccross-section) and has 1, 2, 3 or 4 C-shaped or concave geometries along1, 2, 3 or 4 sides of the parallelogram (FIG. 10).

In this embodiment the acute angle is different or the same along thelength of the file. If the acute angle is different along the length ofthe file; preferably the acute angle is larger at the tip and decreasesas it approaches the shank. For example, the tip cross section has anacute angle of 80 degrees and decrease to an acute angle of 70 degreesas it approaches the shank (FIG. 11).

It is contemplated that the angles located proximate to the tip portionmay be at least about 60 degrees and preferably at least about 65degrees. Furthermore, the angle proximate to the tip portion may be lessthan about 85 degrees, and preferably less than about 80 degrees. Forexample, the angles located proximate to the tip portion may range fromabout 60 to about 85 degrees and preferably from about 65 to about 80degrees. It is further contemplated that the angles located distally(toward the shank) from the tip portion may be at least about 40 degreesand preferably at least about 50 degrees. Furthermore, the angle locateddistally (toward the shank) from the tip portion may be less than about85 degrees, and preferably less than about 80 degrees. For example, theangles located distally (toward the shank) from the tip portion mayrange from about 40 to about 85 degrees and preferably from about 50 toabout 80 degrees.

The lengths of the parallelogram (both on center and off center) maydefine various desirable ratios (e.g., from about 2:1 to about 1:4, fromabout 2:1 to about 1:2, from about 1:2 to about 1:1, from about 1:2 toabout 4:5) of the helical angles between the acute angle helical angleand the obtuse angle helical angle, the helical angles between a firstacute angle helical angle and an adjacent second acute angle helicalangle, the helical angles between a first obtuse angle helical angle andan adjacent second obtuse angle helical angle, and/or the offset heightsbetween the acute angle cutting edge and the obtuse angle cutting edge.It is appreciated that in one embodiment, the ratio of the lengths ofthe edges of the parallelogram may be about 1 (e.g., for the on centerdesign) and/or, the ratio may range from about 1.6 to about 1.1 (e.g.,for the off center parallelogram).

In another embodiment, the ratio of the acute angle helical angle andthe obtuse angle helical angle may range from about 1.8 to about 1.2(e.g., for the on center design) and/or the ratio may range from about1.7 to about 1.1 (e.g., for the off center parallelogram).

In yet another embodiment, the offset heights between the acute anglecutting edge and obtuse angle cutting edge may vary from about 0.17 mmto about 0.05 mm (e.g., for the on center design), and/or the heightsmay vary from about 0.15 mm to about 0.1 mm (e.g., for the off centerparallelogram).

Superelastic materials are typically metal alloys, which return to theiroriginal shape after substantial deformation. Examples of efforts in theart towards superelastic materials are found in U.S. Pat. No. 6,149,501,which is herein incorporated by reference for all purposes.

The endodontic instruments disclosed above can be made of shape memoryalloys (e.g., NiTi based, Cu based, Fe based, or combinations thereof)in their martensitic state of the present invention may provide moreflexibility and increase fatigue resistance by optimized microstructure,which is particularly effective in shaping and cleaning canals withsevere curvatures. Superelastic alloys such as nickel titanium (NiTi) orotherwise can withstand several times more strain than conventionalmaterials, such as stainless steel, without becoming plasticallydeformed.

This invention relates to dental instruments disclosed above.Specifically, this invention relates to endodontic rotary instrumentsfor use in root canal cleaning and shaping procedures. The presentinvention provides an innovation of endodontic instrument that is madeof shape memory alloys (SMA) such as Nickel-Titanium (NiTi) basedsystems, Cu based systems Fe based systems, or any combination thereof(e.g., materials selected from a group consisting of near-equiatomicNi—Ti, Ni—Ti—Nb alloys, Ni—Ti—Fe alloys, Ni—Ti—Cu alloys, beta-phasetitanium and combinations thereof).

The present invention comprises rotary instruments made of NiTi ShapeMemory Alloys, which provide one or more of the following novel aspects:

Primary metallurgical phase in microstructure: martensite is the primarymetallurgical phase in the present invention instrument, which isdifferent from standard NiTi rotary instruments with predominantaustenite structure at ambient temperature.

Higher austenite finish temperature (the final A.sub.f temperaturemeasured by Differential Scanning calorimetry): the austenite finishtemperature is preferably higher (e.g., at least about 3.degree. C.)than the ambient temperature (25.degree. C.); in contrast, most standardsuperelastic NiTi rotary instruments have austenite finish temperatureslower than ambient temperature.

Due to higher austenite finish temperature, the present inventioninstrument would not return to the original complete straight stateafter being bent or deflected; in contrast, most standard superelasticNiTi rotary instruments can return to the original straight form viareverse phase transformation (martensite-to-austenite) upon unloading.

Endodontic instruments made of NiTi shape memory alloys in theirmartensitic state have significantly improved overall performance thantheir austenitic counterparts (regular superelastic NiTi instruments),especially on flexibility and resistance against cyclic fatigue.

The strength and cutting efficiency of endodontic instruments can alsobe improved by using ternary shape memory alloys NiTiX (X: Co, Cr, Fe,Nb, etc) based on the mechanism of alloy strengthening.

Specifically, the present invention instrument has essential and mostdesired characteristics for successful root canal surgery, includinghigher flexibility and lower stiffness, improved resistance to cyclicfatigue, higher degree of rotation against torsional fracture, moreconforming to the shape of highly curved canals (less likely for ledgingor perforation), and minimum possibility of instrument separation incomparison against conventional endodontic instruments made of NiTishape memory alloy in superelastic condition with fully austenitic phasein microstructure.

Example #1 (on Center File Designs)

30.06 ISO Tapered files were manufactured with parallelogram-shapedcross sections with constant angles (e.g., constant acute anglesgenerally throughout the working portion of the file). Table 1 providesthe measured cutting efficiency for the on center file designs of thesetapered files with parallelogram-shaped cross sections with constantangles as compared to a triangle cross section ISO Tapered file (Vortex). . . .

TABLE 1 Average Cutting Was it more efficient than File Efficiency(mm/sec) 30.06 Vortex? 80 Deg. 30.06 0.304 No 70 Deg. 30.06 0.443 Yes(by about 10%) 60 Deg. 30.06 0.477 Yes (by about 17%) 65 Deg. 30.060.455 Yes (by about 11%) 75 Deg. 30.06 0.387 Statistically the sameVortex 30.06 (60 Deg) 0.403 —

As shown in Table 1 and Charts 1-3 (FIGS. 14-16) for endodontic fileshaving parallelogram-shaped cross sections with constant angles(generally throughout the working portion of the file), the smaller theparallelogram angle resulted in higher the void volume and highercutting efficiency. The definition of void volume is the amount of freevolume between the file and the canal wall.

Example #2 (on Center File Designs)

30.06 ISO tapered files were manufactured with parallelogram-shapedcross sections with variable angles (e.g., variable acute angles,generally throughout the working portion of the file). Table 2 providesmeasured cutting efficiency for on center file designs of 30.06 ISOTapered files, which were manufactured with parallelogram-shaped crosssections having variable angles as compared to a triangle cross sectionISO Tapered file (Vortex). FIG. 12 provides an example of one of theendodontic files having a parallelogram-shaped cross sections withvariable angles (generally throughout the working portion of the file)

TABLE 2 Design Average Cutting Efficiency (mm/sec) M4 30.06 80-70 deg.0.333 M4 30.06 80-60 deg. 0.432 M4 30.06 70-60 deg. 0.391 M4 30.06 70-50deg. 0.450 30.06 Vortex 0.403

As shown in Table 2: for endodontic files having parallelogram-shapedcross sections with variable angles (generally throughout the workingportion of the file), larger cross section angles results in highercutting efficiency (with the exception of higher angles apically).Furthermore, it is appreciated that larger cross section angles at thetip of the file may reduce void volume while providing more mass at thetip to increase the strength of the file (which reduces file breakage).Desirably, endodontic files having parallelogram-shaped cross sectionswith variable angles (generally throughout the working portion of thefile) include larger cross section angles at or towards the tip portionand lower cross section angles towards the shank.

Example #3 (Off Center File Designs)

30.06 ISO Tapered files were manufactured with parallelogram-shapedcross sections with constant angles and compared to a triangle crosssection ISO Tapered file for cutting efficiency.

As shown in Charts 4-5 (FIGS. 17-18) for off center file designs of30.06 ISO Tapered files, which were manufactured withparallelogram-shaped cross sections having constant angles, smallercross section angles results in higher cutting efficiency and highervoid volume. FIG. 13 provides an example of one of the endodontic files(off center file design) having a parallelogram-shaped cross sectionswith constant angles (generally throughout the working portion of thefile).

Method of Manufacturing

Examples of efforts in the art directed to methods of manufacturingendodontic instruments may be found in, but not limited to U.S. PatentApplication 20110271529, which is herein incorporated by reference forall purposes.

It will be appreciated that functions or structures of a plurality ofcomponents or steps may be combined into a single component or step, orthe functions or structures of one-step or component may be split amongplural steps or components. The present invention contemplates all ofthese combinations. Unless stated otherwise, dimensions and geometriesof the various structures depicted herein are not intended to berestrictive of the invention, and other dimensions or geometries arepossible. In addition, while a feature of the present invention may havebeen described in the context of only one of the illustratedembodiments, such feature may be combined with one or more otherfeatures of other embodiments, for any given application. It will alsobe appreciated from the above that the fabrication of the uniquestructures herein and the operation thereof also constitute methods inaccordance with the present invention. The present invention alsoencompasses intermediate and end products resulting from the practice ofthe methods herein. The use of “comprising” or “including” alsocontemplates embodiments that “consist essentially of” or “consist of”the recited feature.

The explanations and illustrations presented herein are intended toacquaint others skilled in the art with the invention, its principles,and its practical application. Those skilled in the art may adapt andapply the invention in its numerous forms, as may be best suited to therequirements of a particular use. Accordingly, the specific embodimentsof the present invention as set forth are not intended as beingexhaustive or limiting of the invention. The scope of the inventionshould, therefore, be determined not with reference to the abovedescription, but should instead be determined with reference to theappended claims, along with the full scope of equivalents to which suchclaims are entitled. The disclosures of all articles and references,including patent applications and publications, are incorporated byreference for all purposes.

1. A rotatable endodontic file for cleaning/shaping a tooth root canal,comprising: an elongated shaft having a proximal end portion, a distalend and a tapered working portion having a rotational axis, the workingportion extending from said proximal portion to said distal end; theexternal surface of said shaft working portion having a plurality of atleast two spirals, a plurality of parallelogram-shaped cross sectionsalong the working portion, at least one of the plurality ofparallelogram-shaped cross sections two C-shaped or concave geometriesalong two symmetrical sides or four C-shaped or concave geometries alongall four sides, each parallelogram-shaped cross section having an acuteangle and a center of mass that is located on the axis of rotation, eachparallelogram-shaped cross section, wherein an acute angle of a firstparallelogram-shaped cross section is different or the same as an acuteangle of a second parallelogram-shaped cross section.
 2. An endodonticfile according to claim 1, wherein the acute angle of the firstparallelogram-shaped cross section is larger towards the proximal endthan the acute angle of the second parallelogram-shaped cross sectiontowards the distal end.
 3. An endodontic file according to claim 2,wherein the acute angles of the first and second parallelogram-shapedcross section range between 50 degrees and 85 degrees.
 4. An endodonticfile according to claim 1, wherein the acute angles of the first andsecond parallelogram-shaped cross section range between 50 degrees and85 degrees.
 5. An endodontic file according to claim 1, wherein the fileis composed of a material selected from the group consisting of aNitinol based material, Cu based material, titanium based material and astainless steel based material.
 6. An endodontic file according to claim5, wherein the material is processed by high temperature, coldtemperatures and/or strain.
 7. A rotatable endodontic file forcleaning/shaping a tooth root canal, comprising: an elongated shafthaving a proximal end portion, a distal end and a tapered workingportion having a rotational axis, the working portion extending fromsaid proximal portion to said distal end; the external surface of saidshaft working portion having a plurality of at least two spirals, aplurality of parallelogram-shaped cross sections that extend along theworking portion, at least one of the parallelogram-shaped cross sectionshaving one, two, three, or four C-shaped or concave geometries alongone, two, three, or four sides, wherein each parallelogram-shaped crosssection having an acute angle and a center of mass is not located on theaxis of rotation, and wherein an acute angle of a firstparallelogram-shaped cross section is different or the same as an acuteangle of a second parallelogram-shaped cross section.
 8. An endodonticfile according to claim 7, wherein the acute angle of the firstparallelogram-shaped cross section is larger towards the proximal endthan the acute angle of the second parallelogram-shaped cross sectiontowards the distal end.
 9. An endodontic file according to claim 8wherein the acute angles of the first and second parallelogram-shapedcross section range between 50 degrees and 85 degrees.
 10. An endodonticfile according to claim 7 wherein the acute angles of the first andsecond parallelogram-shaped cross section range between 50 degrees and85 degrees.
 11. An endodontic file according to claim 7, wherein thefile is composed of a material selected from the group consisting of aNitinol based material, Cu based material, titanium based material and astainless steel based material.
 12. An endodontic file according toclaim 11 wherein the material is processed by high temperature, coldtemperatures and/or strain.